11. Consider the 23 letters of the classical Latin alphabet: (6 points) A, B, C, D, E, F, G, H, I, K, L, M, N, O, P, Q, R, S, T, V, X, Y, Z (a) How many strings of length 12 that include the substring SPQR can be formed from the classical Latin alphabet without any repetitions? (b) How many characters are guaranteed to be the same letter within a string of length 52 that has been formed from the classical Latin alphabet? (c) Numerous modern alphabets descend from this one. How many ways can 7 letters be selected from the classical Latin alphabet for inclusion in a new alphabet? [Note: Assume that the relative order of the 7 selected letters must be preserved. For example, if both 'A' and 'Z' are selected, then 'A' must remain before Z.]